Capacitors comprising organized assemblies of carbon and non-carbon compounds

ABSTRACT

This invention relates generally to capacitors comprising organized assemblies of carbon and non-carbon compounds. This invention further relates to methods of making such organized structures. It also relates to devices containing such structures. In preferred embodiments, the organized structures of the instant invention take the form of nanorods or their aggregate forms. More preferably, a nanorod is made up of a carbon nanotube filled, coated, or both filled and coated by a non-carbon material. In particular, the present invention is directed to a capacitor electrode comprising a carbon nanotube filled with one or more non-carbon materials comprising titanium, a titanium compound, manganese, a manganese compound, cobalt, nickel, palladium, platinum, bromine, iodine, an interhalogen compound, or the combination thereof.

This application is a continuation of U.S. application Ser. No.13/084,492, filed Apr. 11, 2011; which is a continuation of U.S. patentapplication Ser. No. 12/854,757, filed Aug. 11, 2010; which is acontinuation of U.S. patent application Ser. No. 12/045,551, filed Mar.10, 2008, now U.S. Pat. No. 7,794,840; which claims the benefit of U.S.Provisional Application No. 60/918,129 filed on Mar. 15, 2007. Thecontents of the above-identified applications are incorporated herein byreference in their entirety.

TECHNICAL FIELD

This invention relates generally to capacitors and capacitor electrodescomprising organized assemblies of carbon and non-carbon compounds. Inparticular, the present invention is directed to a capacitor electrodecomprising a carbon nanotube filled with one or more non-carbonmaterials comprising titanium, a titanium compound, manganese, amanganese compound, cobalt, nickel, palladium, platinum, bromine,iodine, an interhalogen compound, or the combination thereof.

BACKGROUND OF THE INVENTION

There are numerous potential applications of carbon nanotubes (CNTs)because of their unique mechanical, physical, electrical, chemical, andbiological properties. For example, ultra low resistance conductors,semiconductors, highly efficient electron emitters, ultra-stronglightweight fibers for structural applications, lasers, and gas sensorscan all be manufactured by using CNTs.

A variety of synthesis techniques for preparing CNTs exist. Thesetechniques include for example carbon arc, laser ablation, chemicalvapor deposition, high pressure carbon monoxide process (HiPco),cobalt-molybdenum catalyst process (CoMoCat). Depending on thepreparation method, CNTs may be metallic and semiconducting.

The incorporation of non-carbon materials into CNTs may lead to evenmore diverse range of applications, for example, in improved gaseousstorage media or electronic devices. In a publication entitled“Titanium-Decorated Carbon Nanotubes as a Potential High-CapacityHydrogen Storage Medium”, Physical Review Letters, 2005, Vol. 94, pages175501-1 to 175501-4, Yildirim et al. describe that each titanium atomadsorbed on a single-wall CNT (SWCNT) may theoretically bind up to fourhydrogen molecules.

In a publication entitled “Titanium Monomers and Wires Adsorbed onCarbon Nanotubes: A First Principles Study”, Nanotechnology, 2006, Vol.17, pages 1154-1159, Fagan et al. describe a theoretical study of Timonomers and wires interacting with a semiconductor single-wall carbonnanotube, by inside as well as outside faces. Fagan et al. only providea theoretical study without actual data.

Electrochemical supercapacitors based on high surface area carbon havebeen demonstrated since the late fifties. However, only in the ninetiesdid supercapacitors become important, particularly for the developmentof fuel cell and hybrid electric vehicles. This is because a capacitorcan discharge and recharge far faster than a battery, making it idealboth for generating bursts of speed and for soaking up the energycollected by regenerative braking of the vehicle. Capacitors may thus beable to bridge the gap that exists between speed and endurance.

Therefore, there exists a need for new or improved capacitors forproviding high capacitance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of the types of the organized carbon andnon-carbon assemblies of the instant invention.

FIG. 2 shows variation of Specific Current of the organized carbon andnon-carbon assemblies as a function of the applied potential.

FIG. 3 shows variation of Specific Current of the organized carbon andnon-carbon assemblies as a function of the applied potential.

FIG. 4 shows variation of Specific Current of the organized carbon andnon-carbon assemblies as a function of the applied potential.

FIG. 5 shows variation of capacitance of the organized carbon andnon-carbon assemblies as a function of the applied potential.

FIG. 6 shows variation of capacitance of the organized carbon andnon-carbon assemblies as a function of the applied potential.

FIG. 7 shows variation of capacitance of the organized carbon andnon-carbon assemblies as a function of the applied potential.

SUMMARY OF THE INVENTION

The present invention is directed to a capacitor or a capacitorelectrode comprising organized carbon and non-carbon assemblies. Inparticular, the present invention is directed to a capacitor electrodecomprising a carbon nanotube filled with one or more non-carbonmaterials comprising titanium, a titanium compound, manganese, amanganese compound, cobalt, nickel, palladium, platinum, bromine,iodine, an interhalogen compound, or the combination thereof. A titaniumcompound may have a formula TiH_(w)B_(x)N_(y)O_(z), wherein w=0 to 2,x=0 to 2, y=0 to 1, and z=0 to 2. The titanium compound may also be amixture of titanium and bismuth. The manganese compound may have aformula MnH_(w′)B_(x′)N_(y′)O_(z′), wherein w′=0 to 4, x′=0 to 2, y′=0to 1, and z′=0 to 2.

In the capacitor electrode of the present invention, the carbon nanotubemay be a single wall carbon nanotube or a multi wall carbon nanotube.Preferably, the capacitor electrode comprises at least one carbonnanotube.

In the capacitor electrode of the present invention, the filled carbonnanotube is optionally coated with a second non-carbon material.Preferably, the second non-carbon material comprises titanium, atitanium compound, manganese, a manganese compound, cobalt, nickel,palladium, platinum, or the combination thereof.

DETAILED DESCRIPTION OF THE INVENTION

This invention is directed to capacitors comprising organized assembliesof carbon and non-carbon materials. These organized structures are madeup of one or more types of a repeating unit that is shorter in onedimension than the other dimensions and may adopt different shapes, suchas a rod, spherical, semi-spherical, or egg shape. The shorter dimensionis typically less than 1,000 nm, preferably less than 100 nm, or morepreferably less than 10 nm. A cross-section of a repeating unit mayresemble a circular, oval, or rectangular shape. Typically, individualrepeating units (or different types of repeating units) aggregate tonanometer size fragments. In preferred embodiments, a repeating unit ofthis invention may be a nanorod comprising nano carbon and non-carbonmaterials.

Many forms of carbon are suitable for this invention. These forms ofcarbon include for example amorphous carbon, graphite, MWCNT, SWCNT, ora mixture thereof. In preferred embodiments of this invention, thecarbon may be MWCNT, SWCNT, or a mixture thereof.

Many non-carbon materials are suitable for this invention. Non-carbonmaterials may be metal (or metal compounds) or non-metal. For example, anon-carbon material may comprise a metal, a metal compound, metalnitride, metal oxide, metal hydride, metal boride, bromine, iodine,interhalogen compounds, or mixture (or alloy) thereof. Some examples ofa non-carbon material include magnesium (Mg), magnesium hydride (MgH₂),magnesium diboride (MgB₂), magnesium nitride (Mg₃N₂), magnesium oxide(MgO), strontium (Sr), scandium (Sc), scandium nitride (ScN), yttrium(Y), titanium (Ti), titanium hydride (TiH₂), titanium nitride (TiN),titanium diboride (TiB₂), titanium oxide (TiO₂), zirconium (Zr),zirconium diboride (ZrB₂), zirconium nitride (ZrN), hafnium (Hf),hafnium nitride (HfN), vanadium (V), vanadium diboride (VB₂), niobium(Nb), niobium diboride (NbB₂), niobium nitride (NbN), tantalum (Ta),chromium (Cr), chromium diboride (CrB₂), manganese (Mn), iron (Fe),cobalt (Co), nickel (Ni), palladium (Pd), platinum (Pt), boron (B),boron hydrides, boron nitride (BN), boron oxide (B₂O₃), bromine (Br₂),iodine (I₂), and a mixture (or alloy) thereof. In addition, thenon-carbon material may be amorphous or crystalline. The crystallineform could be distorted, for example by having deficiencies in thecrystal structure.

Particularly, the present invention is directed to a capacitor electrodecomprising repeating units of a carbon nanotube filled with one or morenon-carbon materials comprising titanium, a titanium compound,manganese, a manganese compound, cobalt, nickel, palladium, platinum,bromine, iodine, an interhalogen compound, or the combination thereof.

In one embodiment of this invention, the non-carbon material comprisestitanium or a titanium compound. A titanium compound, as used herein,refers to a compound that contains titanium. For example, a titaniumcompound may be a titanium hydride, titanium boride, titanium nitride,titanium oxide, or a mixture thereof. In particular, a titanium compoundmay be abbreviated with a formula TiH_(w)B_(x)N_(y)O_(z), where w variesin the range of 0 to 2, x varies in the range of 0 to 2, y varies in therange of 0 to 1, and z varies in the range of 0 to 2. The titaniumcompound may also be a mixture (or an alloy) of titanium with bismuth.

In another embodiment of this invention, the non-carbon materialcomprises manganese or a manganese compound. A manganese compound, asused herein, refers to a compound that contains manganese. For example,a manganese compound may be a manganese hydride, nitride, oxide, or amixture thereof. In particular, a manganese compound may be abbreviatedwith a formula MnH_(w′)B_(x′)N_(y′)O_(z′), where w′ varies in the rangeof 0 to 4, x′ varies in the range of 0 to 2, y′ varies in the range of 0to 1, and z′ varies in the range of 0 to 2.

In yet another embodiment of this invention, the non-carbon materialcomprises bromine, iodine, an interhalogen compound, or mixturesthereof. An interhalogen compound, as used herein, is a compound thatcontains two or more halogens, such as IBr, ICl₃ and BrF₃.

The non-carbon material may also comprise limited amount of metalcarbides, such as titanium carbide, silicon carbide, vanadium carbide,tantalum carbide, or a mixture thereof with an amount less than 10volume percent.

As a repeating unit, the non-carbon material may fill, coat, or bothfill and coat the carbon material. These three cases are schematicallyshown in FIG. 1 (a) to (c). In the first case shown in FIG. 1( a), thenon-carbon material fills the core of the carbon. The articles of thefirst case are abbreviated hereafter as “non-carbon material filledcarbon,” for example, as Ti filled SWCNT. In the second case shown inFIG. 1( b), the non-carbon material coats the carbon. The articles ofthis case are hereafter abbreviated as “non-carbon material coatedcarbon,” for example, as Ti coated SWCNT. In the third case shown inFIG. 1( c), the non-carbon material both fills and coats the carbon. Thearticles of this case are hereafter abbreviated as “non-carbon materialfilled and coated carbon,” for example, as Ti filled and coated SWCNT.

The repeating unit may be partially hollow. For example, the core of aSWCNT may be partially empty. The empty portion of the core may be lessthan 95, 75, 50, 25, or 10 volume percent. The coating, filling, orcoating and filling by the non-carbon material may have a continuous ornon-continuous form. For example, they may be in the form of acontinuous film deposited on the outer or inner surface of a SWCNT,islands deposited on the outer or inner surface of a SWCNT, beadsdeposited on the surface of a SWCNT, or particulates deposited in thecore of a SWCNT.

The instant invention is also directed to a method for preparing theorganized assembly of carbon and non-carbon materials.

The method comprises a step of reacting a carbon precursor with ahalogenated precursor to generate a halogenated intermediate. Ahalogenated precursor may comprise a halogenated compound, such asmagnesium iodide (MgI₂), scandium iodide (ScI₃), scandium bromide(ScBr₃), titanium iodide (TiI₄), titanium bromide (TiBr₄), vanadiumiodide (VI₃), vanadium bromide (VBr₃), iron iodide (FeI₂), cobalt iodide(CoI₂), nickel iodide (NiI₂), palladium iodide (PdI₂), platinum iodide(PtI₂), boron iodide (BI₃), or a mixture thereof. The amount of thehalogenated compound in a halogenated precursor may be at least 0.001weight %, 0.01 weight %, 0.1 weight %, 1 weight %, 10 weight %, 50weight %, or 80 weight %.

In another embodiment, a halogenated precursor suitable for thisinvention may comprise a halogen, such as iodine, bromine, aninterhalogen compound (such as IBr, ICl₃, BrF₃), or a mixture thereof.The amount of halogen in a halogenated precursor may be at least 0.001weight %, 0.01 weight %, 0.1 weight %, 1 weight %, 10 weight %, 50weight %, or 80 weight %.

In addition to the above-described active ingredients, a halogenatedprecursor may also comprise inactive ingredients such as inert diluents,impurities, etc.

The halogenated intermediate may be used as obtained after the reactionof carbon precursor with a halogenated precursor to prepare thecapacitor electrodes of the instant invention. As an optional step, thehalogen is removed from the halogenated intermediate before the step ofpreparation of the capacitors. If the non-carbon includes a hydride,nitride, oxide, or a mixture thereof, the method may further comprisesthe step of hydrogenation, nitrogenation, and/or oxidation after thehalogen removal step to obtain a composition comprising (1) carbon and(2) a non-carbon hydride, nitride, oxide, or a mixture thereof.

Many forms of the carbon precursor are suitable for this invention.These forms of carbon precursors include for example amorphous carbon,graphite, MWCNT, SWCNT, or a mixture thereof. In preferred embodimentsof this invention, the carbon may be MWCNT, SWCNT, or a mixture thereof.

A SWCNT precursor suitable for this invention may be prepared by anysynthesis method. Such methods may include, but are not limited to,carbon arc, laser vaporization, chemical vapor deposition (CVD), highpressure carbon monoxide process (HiPco), cobalt-molybdenum catalystprocess (CoMoCat). A SWCNT precursor may be a mixture of SWCNTprecursors prepared by more than one synthesis method.

In one embodiment, the SWCNT precursor is used as purchased for themethod disclosed in this invention. In another embodiment, amorphouscarbons and/or catalysts is removed from the as-purchased SWCNTs beforethe application of the disclosed method. The amorphous carbon and/or thecatalyst removal may be complete or partial. Thus, a SWCNT precursor maycontain any level of amorphous carbon and/or catalyst. The invention isnot limited to any particular method of removing the amorphous carbonand/or the catalyst from the starting SWCNTs. As an example, the methoddisclosed by Delzeit et al. in U.S. Pat. No. 6,972,056 may be used forthis removal.

As a first process step, a carbon precursor is reacted with ahalogenated precursor. This reaction results in the incorporation of thecarbon precursor with the halogenated precursor to form a halogenatedintermediate. This incorporation may be in any form. For example, thehalogen may be incorporated on the outer or inner surface or into thechemical structure of the carbon precursor. This incorporation may bethrough chemical or physical bonding.

The amount of non-carbon material present in the halogenated precursorcontrols the amount of non-carbon material incorporated into theassembly. Thus, by varying the ratio of the non-carbon material amountto the carbon precursor, the non-carbon material content of the finalcomposition can be varied. The ratio of non-carbon material present inthe halogenated precursor to carbon present in the carbon precursor maybe at least 0.01 weight %, 1 weight %, 10 weight %, or 25 weight %.

The reaction between the carbon precursor and the halogenated precursormay occur at a temperature at which the halogenated precursor is aliquid. Typically, it is at or above the melting temperature of thehalogenated precursor. For example, if the halogenated precursor isabout 100 weight % TiI₄, the reaction may be carried out at atemperature above the melting point of TiI₄, which is about 150° C. When100% TiBr₄ is a halogenated precursor, the reaction temperature may beabove the melting point of TiBr₄, i.e., about 28° C. As another example,if the precursor is a mixture of a halogenated compound and a halogen,the reaction may be carried out at or above a temperature at which thismixture forms a liquid. For example, when a mixture of TiI₄ and I₂ is ahalogenated precursor, the reaction may be carried out at a temperatureabove the melting point of iodine, i.e., about 113.6° C. Since bromineis liquid at room temperature, the reaction may be carried out at atemperature above 20° C. when a mixture of a halogenated compound andbromine is used as the halogenated precursor. In different embodiments,the carbon precursor and the halogenated precursor may be reacted at atemperature above 20° C., 100° C., 150° C., or 200° C. for a periodlonger than 1 minute, 10 minutes, or 20 minutes.

After reacting the carbon precursor with the halogenated precursor, ahalogenated intermediate is produced. This halogenated intermediate maybe used directly in preparation of the capacitors of the instantinvention. For example, bromine filled SWCNTs may be used in preparationof such capacitors.

Optionally, the carbon precursor may be heated above room temperature toremove volatile compounds, such as water, before reacting with thehalogenated precursor. The volatile compound removal may be achieved byheating the carbon precursor above 100° C. or 200° C. for a periodlonger than 10 minutes.

As another optional process step, halogen is removed from thehalogenated intermediate. During the reaction between the carbonprecursor and the halogenated precursor, the halogenated precursor mayintercalate between layers of the carbon precursor, open the end caps ofthe carbon nanotubes and fill their cores, coat the carbon precursor, orboth fill (i.e. intercalate) and coat the carbon precursor. As a result,the halogenated intermediate may contain halogen, in a free form, suchas iodine, and/or in a form of a halogenated compound, such as TiI₄. Itmay be necessary to reduce the halogen level of the organized assemblyto prepare a capacitor with desired properties. The halogen removal maybe achieved by sublimation, evaporation, or thermal degradation. Thehalogen removal may also be achieved by reacting the halogenatedintermediate with a suitable reactant, for example, hydrogen.

In particular, the halogen removal step may comprise heating thehalogenated intermediate at a temperature for a period sufficient enoughto reduce the halogen content of the intermediate below 10 weight %. Forexample, the halogen removal step may be carried out at a temperatureabove 200° C., 300° C., 500° C., or 800° C. for a period longer than 5minutes, 10 minutes, 30 minutes, or 1 hour. In one embodiment, thisheating may be carried out in a gas mixture comprising hydrogen at atemperature for a period sufficient enough to reduce the halogen contentof the intermediate below 10 weight %. For example, the heating step maybe carried out in a gas mixture comprising at least 0.01 volume % or 1volume % hydrogen at a temperature above 200° C., 300° C., 500° C., or800° C. for a period longer than 5 minutes, 10 minutes, 30 minutes, or 1hour. The heating may be carried out below 1 atmosphere pressure.

After the halogenation removal step, an organized assembly comprising acarbon and a non-carbon material (such as metal, metal like compound,metal boride, bromine or a mixture thereof) is obtained. Specificexamples of such non-carbon material include magnesium (Mg), magnesiumdiboride (MgB₂), strontium (Sr), scandium (Sc), yttrium (Y), titanium(Ti), titanium diboride (TiB₂), zirconium (Zr), zirconium diboride(ZrB₂), hafnium (Hf), hafnium nitride (HfN), vanadium (V), vanadiumdiboride (VB₂), niobium (Nb), niobium diboride (NbB₂), tantalum (Ta),chromium (Cr), chromium diboride (CrB₂), manganese (Mn), iron (Fe),cobalt (Co), nickel (Ni), palladium (Pd), platinum (Pt), boron (B),boron nitride (BN), bismuth (Bi), bromine, iodine, interhalogencompounds, and a mixture (or alloy) thereof.

For an organized assembly comprising (1) a carbon and (2) a non-carbonhydride, boride, nitride, oxide, or a mixture thereof, the methodfurther includes hydrogenation, reaction with boron compounds,nitrogenation, and/or oxidation of the product after the halogen removalstep. The hydrogenation may be carried out above room temperature in agas mixture containing hydrogen, ammonia, or hydrazine. The reactionwith boron compounds may be carried out by reacting the product withboron hydrides, for example B₂H₆, B₅H₁₁. The nitrogenation may becarried out above room temperature in a gas mixture containing nitrogen,ammonia, hydrazine, or a mixture thereof. The oxidation may be carriedout at room temperature or above in a gas mixture containing oxygen. Asa result of hydrogenation, reaction with boron compounds, nitrogenation,and/or oxidation, the assembly comprising (1) a carbon and (2) anon-carbon (such as metal) hydride, boride, nitride, oxide, or a mixturethereof is formed. Some examples of such non-carbon material includemagnesium hydride (MgH₂), magnesium nitride (Mg₃N₂), magnesium oxide(MgO), scandium nitride (ScN), titanium hydride (TiH₂), titanium nitride(TiN), titanium oxide (TiO₂), zirconium nitride (ZrN), hafnium nitride(HfN), niobium nitride (NbN), boron hydrides, boron nitride (BN), boronoxide (B₂O₃), and a mixture thereof.

In one embodiment of this invention, the organized assembly comprisingnon-carbon material filled and coated carbon, such as Ti filled andcoated SWCNT may be prepared by both filling and coating the carbonnanotube with the halogenated precursor. To achieve the filling, thesize of the core should be larger than that of the halogenatedprecursor. For example, a halogenated compound, TiI₄ has a size of about1 nm. During the halogenation reaction, this compound can fill the coresof SWCNTs that have inner diameters larger than 1 nm. For example, sincethe SWCNTs prepared by the carbon arc process have inner diameterslarger than 1 nm, these SWCNTs may be both filled and coated with TiI₄.After the removal of iodine from the SWCNTs, Ti filled and coated SWCNTsare generated.

In another embodiment, the non-carbon material coated carbon, such as Ticoated SWCNTs may be prepared by coating the carbon nanotube with thehalogenated precursor. To achieve the coating but not filling, the sizeof the core should be smaller than that of the halogenated precursor.For example, a halogenated compound TiI₄ has a size of about 1 nm andthe SWCNTs prepared by CoMoCat process have inner diameters smaller than1 nm. Therefore, during the halogenation reaction, TiI₄ coats but doesnot fill the cores of these SWCNTs. After the removal of iodine, Ticoated SWCNTs are produced.

In yet another embodiment, the non-carbon material filled carbon, suchas Ti filled SWCNTs may be prepared by washing the halogenated precursorcoated and filled carbon nanotubes with a suitable solvent, such asethanol. This washing may remove the halogenated precursor coating, butnot the filling at the carbon nanotube core. Then, after the iodineremoval, Ti filled SWCNTs are produced. This washing may completelyremove the halogenated precursor coating if a suitable solvent is usedand/or if the solvent washing step is repeated several times. Thiswashing may also partially remove the halogenated coating, for example,thereby incorporating a coating that has a particulate form to thecarbon. The amount of the coating then may be varied by controlling thesolvent type, solvent amount, and number of repetition of washing steps.

Thus, by choosing the core size of the carbon nanotube, or byincorporating a solvent wash step when the core size is larger than sizeof the halogenated precursor, the non-carbon materials may fill, coat,and both fill and coat the carbon nanotubes.

In one embodiment of the invention, the method comprises first fillingthe carbon nanotube and then further filling and/or coating the filledcarbon nanotube with a second non-carbon material. The further fillingand/or coating with the second non-carbon may be achieved by followingthe method disclosed above.

This invention is particularly directed to capacitors and capacitorelectrodes comprising the organized carbon and non-carbon assemblies ofthe instant invention. The capacitor may be in any form suitable forstorage of electrical charge. For example, the capacitor may comprisetwo electrodes of equal area arranged in parallel configuration andseparated by a fixed distance, placed in a conducting electrolytesolution, with an insulating material or separator located between thetwo electrodes. There may be many more methods for construction ofcapacitors. All of them are within the scope of this invention.

In the present invention, at least one electrode of the capacitorcomprises the organized carbon and non-carbon assemblies of the instantinvention. In a preferred embodiment of this invention, the capacitorelectrode comprises a carbon nanotube filled with one or more non-carbonmaterials comprising titanium, a titanium compound, manganese, amanganese compound, cobalt, nickel, palladium, platinum, bromine,iodine, an interhalogen compound, or the combination thereof.

In one embodiment, the non-carbon material comprises titanium.

In another embodiment, the non-carbon material comprises a titaniumcompound. The titanium compound may have a formula ofTiH_(w)B_(x)N_(y)O_(z), wherein w=0 to 2, x=0 to 2, y=0 to 1, and z=0 to2. The titanium compound may also be a mixture of titanium and bismuth.

In another embodiment, the non-carbon material comprises manganese.

In a further embodiment, the non-carbon material comprises a manganesecompound. The manganese compound may have a formulaMnH_(w′)B_(x′)N_(y′)O_(z′), wherein w=0 to 4, x=0 to 2, y=0 to 1, andz=0 to 2.

In a further embodiment, the non-carbon material comprises bromine,iodine, interhalogen compounds, or the combination thereof.

In the above-described capacitor electrode, the filled carbon nanotubeis optionally coated with a second non-carbon material. Many non-carbonmaterials are suitable for coating. For example, the filled nanotubesmay be coated with a non-carbon materials such as titanium, a titaniumcompound, manganese, a manganese compound, nickel, aluminum, tin,selenide, telluride, nickel oxide, cobalt oxide, manganese oxide,ruthenium oxide, osmium oxide, cobalt, nickel, palladium, platinum, orthe combination thereof; with titanium, a titanium compound, manganese,a manganese compound, cobalt, nickel, palladium, platinum beingpreferred. The titanium compound may have a formulaTiH_(w)B_(x)N_(y)O_(z), wherein w=0 to 2, x=0 to 2, y=0 to 1, and z=0 to2, or may be a mixture of titanium and bismuth. The manganese compoundmay have a formula MnH_(w′)B_(x′)N_(y′)O_(z′), wherein w=0 to 4, x=0 to2, y=0 to 1, and z=0 to 2.

Capacitance C is proportional to the surface area A of the capacitorelectrode, the dielectric constant ∈ of the electrodes, and inversedistance d between the electrodes:

C=k(∈A)/d

where k is a constant. In this equation, A is not simply the geometricalarea, but it is the entire area of the capacitor material including thearea provided by pores of the capacitor material. In other words, A isthe total area that comes into close contact with the electrolyte.

Currently, there are two major approaches to achieve high capacitance.In the first approach, traditional capacitors are based on high ∈materials filling the space between the capacitor electrodes; however,these materials typically are heavy and have very low A (on the order offew m²/g), resulting in moderate values of capacitance per gram ofmaterial, Farad/gram (F/g). In the second recently introduced approach,capacitors use lightweight, electrically conducting, and extremely highsurface area electrode materials (such as activated carbon, with A>1,000m²/g) to achieve high F/g values; however, E values of these materialsare low (∈<10) and do not contribute significantly to capacitance. Thecapacitors of the second approach are called supercapacitors.

The organized carbon and non-carbon assemblies of the instant inventionare suitable for manufacturing of both types of capacitors. Theseorganized assemblies of the present invention provide the unexpectedadvantages of high electrical conductivity, high E and high surfacearea. The area A of the organized assemblies is in the order of fewhundreds or even thousands m²/g depending on the preparation method. Theinventors have discovered that Ti filled SWCNT, TiH_(x) filled SWCNT, Mnfilled SWCNT, Bi—Ti filled SWCNT, Co filled SWCNT, Ni filled SWCNT, Pdfilled SWCNT, Pt filled SWCNT, and Ti filled and coated SWCNT and Brfilled SWCNT articles, but not Fe filled SWCNT article, provide highercapacitance, and are better capacitors than the starting SWCNT article.

The capacitor electrode of this invention may be prepared by manymethods. In one embodiment of this invention, the electrode comprises arepeating unit of the organized carbon and non-carbon assembly. Forexample, the capacitor electrode comprises a Ti filled SWCNT. A singlerepeating unit of the organized assembly may also work as an electrodeand thereby it is within the scope of this invention. For example, thecapacitor may be one Ti filled SWCNT. The repeating unit may also becombined with other materials, for example with polymers, metals, ormetal oxides in preparation of the electrode of this invention. Acoating comprising the repeating unit of the organized assembly on asuitable substrate (for example, aluminum platelet) may also form thecapacitor electrode.

The invention is illustrated further by the following examples that arenot to be construed as limiting the invention in scope to the specificprocedures or products described in them.

EXAMPLES Example 1 Ti Filled SWCNT Articles

In this example, the single-wall carbon nanotubes (SWCNTs) were filledwith titanium (Ti). This experiment was conducted with minimal exposureto the external environment. SWCNTs were purchased from Carbon SolutionsInc. (Riverside, Calif.) with a catalog number P2-SWNT. They weremanufactured by using the arc process. These SWCNTs are designated as“starting SWCNT.”

The starting SWCNTs were processed as follows. The SWCNTs, weighed about1000 mg, were placed in a 50 ml three-necked round bottom Pyrex flask,which was equipped with a heating mantle, a thermocouple, and anaddition arm. The flask was connected to a vacuum system through aliquid nitrogen trap.

The titanium iodide crystals (TiI₄) used in this Example were purchasedfrom Aldrich with a catalog number 41,359-3. The iodine crystals (I₂)were purchased from Aldrich with a catalog number 20,777-2. TiI₄ (about2.7 grams) was mixed with I₂ (about 2.7 grams) in a nitrogen-filledglove box and placed in the flask addition arm. The end of the additionarm was covered to protect the mixture from atmospheric moisture. Theaddition arm was then taken out of the glove box and connected to thereaction flask. Thus, the SWCNTs and the TiI₄/I₂ mixture initially werekept in separate locations in the flask.

After the connection, the flask was immediately evacuated to a pressurebelow 1 Torr. The contents of the flask were then heated to about 150°C. in vacuum for about 15 minutes to remove volatile species from theSWCNTs. After this heating, the vacuum valve was closed and the TiI₄/I₂mixture was poured on the SWCNTs by tipping the addition arm. Theheating was continued to melt the TiI₄/I₂ mixture and soak the SWCNTs inthe melt as follows. First, after the mixture was poured, the flask washeated to about 200° C. within about 6 minutes. Then, it was furtherheated to about 275° C. within about 12 minutes. Upon reaching about275° C., the vacuum valve was opened to remove some un-reacted TiI₄/I₂by evaporation into the cold trap. The heating was continued in vacuumat about 275° C. for about 1 hour. The contents of the flask were thencooled to the room temperature by cutting power to the heating mantle.At this step, the nanorods comprised TiI₄/I₂ coated and filled SWCNTs.

This article was processed to remove TiI₄ and I₂ coating by an ethanolwashing step as follows.

After the cooling, the flask was transferred to the glove box kept innitrogen, and the article was washed with ethanol (Aldrich, catalognumber 45,984-4) to further remove un-reacted TiI₄/I₂ mixture, asfollows. The nanorods were first mixed with about 25 ml ethanol toprepare a suspension. This suspension was then centrifuged at acentrifugal force of about 10,000 g for about 15 minutes to obtain asupernatant phase and a precipitate phase. The supernatant phase wascarefully removed by using a pipette and discarded. This washing stepwas repeated once. The precipitate phase was then transferred back tothe glove box and it was dried at about 25° C. to remove residualethanol. In the ethanol washing step, the centrifugation step may bereplaced with a filtration step to recover the nanorods from thesuspension. At this step, the nanorods comprised TiI₄/I₂ filled SWCNTs.

The TiI₄/I₂ filled SWCNTs were processed to remove iodine by a heattreatment step as follows.

The precipitate phase was then placed in a quartz tube, which wasinserted in a tube furnace. The tube was sealed, connected to a vacuumsystem and evacuated to about 30 mTorr pressure. The furnace was thenheated to about 500° C. within one hour. The heating was continued atabout 500° C. for about 30 minutes.

After this heating period, a gas mixture consisting essentially of about3% hydrogen and about 97% argon was introduced into the quartz tube andthe pressure was raised to about 10 Torr. The heating was furthercontinued at a furnace temperature of about 500° C. for about two hoursat about 10 Torr in the flowing gas mixture, after which the furnace wascooled to room temperature. The Ti filled SWCNTs were thereby obtained.

Example 2 TiH_(x) Filled SWCNT Articles

In this Example, TiH_(x) filled SWCNTs were prepared. First, Ti filledSWCNTs were prepared in the same manner as described in Example 1,except that about 82 mg of SWCNT was used instead of about 1000 mg ofSWCNT, about 1.8 grams of TiI₄ and about 1.8 grams of I₂ were usedinstead of about 2.7 grams of TiI₄ and about 2.7 grams of I₂. Then,these nanorods were placed in an air free chamber and heated to about650° C. in vacuum for at least 2 hours to remove volatile compounds.After the removal of volatile compounds, the temperature was decreasedto about 500° C. and the chamber was pressurized to about 500 Torr withhydrogen. The nanorods were hydrogenated by keeping them at thistemperature for at least one hour. Finally, the hydrogenated nanorodswere cooled to a room temperature. TiH_(x) filled SWCNT articles werethereby prepared.

Example 3 Fe Filled SWCNT Articles

This Example was carried out in the same manner as described in Example1, except that about 0.9 gram of ferric iodide and about 1.8 grams ofiodine were used instead of about 2.7 grams of TiI₄ and about 2.7 gramsof I₂, that the annealing was carried out at about 500° C. for about 30minutes, followed by about 600° C. for about 2 hours instead of about500° C. for about 2 hours, and that during the cooling, a gas mixtureconsisting essentially of about 50 percent nitrogen, about 2.5 percenthydrogen and about 47.5 percent argon was flowed at a pressure of about20 Torr, instead of the gas mixture consisting essentially of about 3percent hydrogen and about 97 percent argon at a pressure of about 10Torr. Fe filled SWCNT articles were thereby prepared.

Example 4 Metal Filled SWCNT Articles

This example was carried out in the same manner as described in Example3, except that iodides of Mn, Co, Ni, Pd, or Pt were used instead offerric iodide. The articles comprising Mn filled SWCNTs, Co filledSWCNTs, Ni filled SWCNTs, Pd filled SWCNTs, or Pt filled SWCNTs werethereby prepared.

Example 5 Bi and Ti Filled SWCNT Articles

In this Example, the Ti filled SWCNT article in Example 1 was furtherprocessed as follows. First, about 100 mg of this article was degassedat about 250° C. for about 30 minutes in vacuum. Then, about 1,000 mg ofbismuth (Bi) powder were added to this article and the temperature wasincreased to about 500° C. and held there for about 18 hours. After thisreaction, the material comprised black and gray granules. The blackgranules were mechanically separated from the gray granules and analyzedby SEM, EDX, and Raman spectroscopy. This analysis indicated that thearticle thereby prepared comprised Bi—Ti filled SWCNTs.

Example 6 Br Filled SWCNT Articles

In this Example, about 400 mg of the starting SWCNT were placed in a 50ml capacity 3-neck flask, equipped with a vacuum pickup, two glassstoppers, and a heating mantle and the flask was immediately evacuatedto a pressure below 1 Torr. The contents of the flask were then heatedto about 150° C.-200° C. in vacuum for about 20 minutes to removevolatile species from the SWCNTs. After the removal of volatiles, theapparatus was cooled to a room temperature and filled with nitrogen.About 10 mL of bromine (99.5+%, Aldrich catalogue number 277576-450G)was then introduced into the flask through an addition funnel. Themixture was magnetically stirred while the temperature of the flask andcontents was raised to a temperature in the range of 40° C. to 59° C.and kept at this temperature for about 2 hours. After this heating, theun-reacted bromine was distilled off at about 100° C. The un-reactedbromine was further removed by evacuating the flask and contents forabout 5 minutes. The article comprising Br filled SWCNTs was therebyprepared.

Example 7 Ti Filled and Coated SWCNT Articles

In this example, the SWCNTs were both filled and coated with titanium(Ti). This example was carried out in the same manner as described inExample 1, except that the contents of the reaction flask were heated atabout 275° C. for about 15 to 20 minutes prior to opening the vacuumvalve and that the ethanol washing step was not carried out after thepreparation of the article comprising TiI₄/I₂ coated and filled SWCNTs.Thus, after the cooling of the flask, TiI₄/I₂ coated and filled SWCNTswere directly placed in a quartz tube, which was inserted in a tubefurnace. The Ti filled and coated SWCNTs were thereby obtained.

Example 8 Capacitance of Organized Assemblies

In this example, twelve electrodes were prepared to determine thecapacitance properties of the organized assemblies. The first electrodewas prepared by using the starting SWCNTs. The second electrode wasprepared by using the Ti filled SWCNT articles prepared in Example 1,the third electrode by using the TiH_(x) filled SWCNT articles preparedin Example 2, the forth electrode by using the Fe filled SWCNT articlesprepared in Example 3, the fifth electrode by using the Mn filled SWCNTarticles prepared in Example 4, the sixth electrode by using the Cofilled SWCNT articles prepared in Example 4, the seventh electrode byusing the Ni filled SWCNT articles prepared in Example 4, the eighthelectrode by using the Pd filled SWCNT articles prepared in Example 4,the ninth electrode by using the Pt filled SWCNT articles prepared inExample 4, the tenth electrode by using the Bi—Ti filled SWCNT articlesprepared in Example 5, eleventh electrode by using the Br filled SWCNTarticles prepared in Example 6, and the twelfth electrode by using theTi filled and coated SWCNT articles prepared in Example 7.

During the preparation of each electrode, the CNT articles were firstsuspended in anhydrous dimethylformamide (DMF), then sonicated using ahorn sonicator (Sonics Materials, Model VC600) for about 15 minutesusing three cycles of about 5 minutes duration (600 W, 20 MHz). Theresulting dispersion was immediately deposited on the surface ofpolished aluminum (Al) plates drop by drop by using a pipette. Thisdeposition formed a thin layer of dispersion on the plates. Eachsubstrate was then heated in an oven at about 130° C. for about 30minutes to remove the solvent. This heating formed a dry coating of theCNT article on the plate. This coating and the aluminum plate formed theelectrode of the instant invention.

The electrochemical properties of each electrode thereby prepared wereanalyzed by cyclic voltammetry (CV) in the standard 3-electrode cellusing an Ag/AgCl, 3 M Cl⁻ reference electrode and a coiled Pt wireauxiliary electrode with a Princeton Applied Research VersaSTAT³Potentiostat/Galvanostat. The capacitor electrolyte was about 0.1 Mtetraethylammonium tetrafluoroborate (TEABF₄) dissolved in propylenecarbonate (PC). In this cell construction, the electrode of theinvention formed the working electrode.

Cyclic voltammograms of the CNT articles in the de-aerated TEABF₄/PCsolution at about 300° Kelvin are shown in FIGS. 2 to 4. Therectangular-shaped profiles obtained at high scan rate (of about 0.05Volts/second) are indicative of rapid charge and discharge processes atthe interface between the nanotube electrodes and the electrolytesolution. From these cyclic voltammograms, the specific capacitance, C(F/g) of each electrode can be obtained using the quantitative equation:

C=i/v

where i is the net current (positive cycle−negative cycle) and v is thepotential scan rate (0.05 Volts/second).

FIGS. 2 to 4 show the specific current profile of the aluminum platewith no CNT article (i.e. bare aluminum plate). For the aluminum plateelectrode, the specific current showed negligible variation with theapplied potential as compared to the electrodes comprising the organizedassemblies. That is, it remained almost flat at about 0 Amperes/g,indicating that it did not have recognizable capacitance as compared tothe electrodes of the instant invention.

FIGS. 5 to 7 show the capacitance of the twelve electrodes measured atabout 300 Kelvin as a function of the applied potential. All theelectrodes comprising the organized assemblies had considerably muchhigher capacitances as compared to the bare aluminum plate. The fillingof Ti, TiH_(x), Mn, Bi—Ti, Co, Ni, Pd, Pt or Br; and filling and coatingof Ti increased the capacitance above that of the electrode prepared byusing the starting SWCNT article. At the potential of about 0 volts, theincorporation of Ti filling resulted in a capacitance gain of about118%, incorporation of Ti filling and coating about 182%, incorporationof TiH_(x) filling about 35%, incorporation of Mn filling about 100%,incorporation of Bi—Ti filling about 142%, incorporation of Br fillingabout 300%, incorporation of Co filling about 165%, incorporation of Nifilling about 105%, incorporation of Pd filling about 35%, andincorporation of Pt filling about 165%. This showed that Ti filledSWCNT, Ti filled and coated SWCNT, TiH_(x) filled SWCNT, Mn filledSWCNT, Bi—Ti filled SWCNT, Br filled SWCNT, Co filled SWCNT, Ni filledSWCNT, Pd filled SWCNT, and Pt filled SWCNT articles are bettercapacitors than the starting SWCNT article.

However, at potential of about 0 volts, the Fe filled SWCNT decreasedthe capacitance below that of the electrode prepared by using thestarting SWCNT article by about 60%. This showed that Fe is not asuitable non-carbon material for preparation of capacitors comprisingthe organized assemblies of the instant invention.

The surface area of several of these articles was measured by theBrunauer, Emmett and Teller method (BET). Nitrogen gas was used as theanalysis gas and BET analysis was done in a P/Po range of 0.05 to 0.99.Table 1 summarizes the BET surface area, the Langmuir surface area andthe micropore volume determined for these articles. As resultsindicated, the articles of the instant invention have large surfacearea, larger than a hundred meters square per gram.

TABLE 1 Surface Area of the Organized Assemblies. BET Langmuir MicroporeSurface Area Surface Area Volume Article (m²/g) (m²/g) (cm³/g) StartingSWCNT 465.7 841.0 0.1015 Ti filled SWCNT 403.3 732.4 0.0835 TiHx filledSWCNT 272.3 519.6 0.0811 Bi—Ti filled SWCNT 365.4 670.2 0.0875

The invention, and the manner and process of making and using it, arenow described in such full, clear, concise and exact terms as to enableany person skilled in the art to which it pertains, to make and use thesame. It is to be understood that the foregoing describes preferredembodiments of the present invention and that modifications may be madetherein without departing from the scope of the present invention as setforth in the claims. To particularly point out and distinctly claim thesubject matter regarded as invention, the following claims conclude thisspecification.

What is claimed is:
 1. A capacitor comprising two capacitor electrodesseparated by an insulating material, wherein at least one of the twocapacitor electrodes comprises a carbon nanotube filled with one or morenon-carbon materials selected from the group consisting of titanium, atitanium compound, manganese, cobalt, nickel, palladium, platinum, andany combination thereof, wherein the filling of the one or morenon-carbon materials in the carbon nanotube increases the capacitance incomparison with the capacitance provided by a capacitor electrodecomprising the same carbon nanotubes but unfilled.
 2. The capacitoraccording to claim 1, wherein said non-carbon material is titanium. 3.The capacitor according to claim 1, wherein said non-carbon material isa titanium compound.
 4. The capacitor according to claim 3, wherein saidtitanium compound has a formula TiH_(w), wherein w=0 to
 2. 5. Thecapacitor according to claim 3, wherein said titanium compound is amixture of titanium and bismuth.
 6. The capacitor according to claim 1,wherein said non-carbon material is manganese.
 7. The capacitoraccording to claim 1, wherein said non-carbon material is cobalt.
 8. Thecapacitor according to claim 1, wherein said non-carbon material isnickel.
 9. The capacitor according to claim 1, wherein said non-carbonmaterial is palladium.
 10. The capacitor according to claim 1, whereinsaid non-carbon material is platinum.
 11. The capacitor according toclaim 1, wherein said carbon nanotube is a single wall carbon nanotube.12. The capacitor according to claim 1, wherein said carbon nanotube isa multi wall carbon nanotube.
 13. The capacitor according to claim 1,wherein said carbon nanotube is further coated with a second non-carbonmaterial.
 14. The capacitor according to claim 13, wherein said secondnon-carbon material comprises titanium, a second titanium compound,manganese, cobalt, nickel, palladium, platinum, or any combinationthereof.
 15. The capacitor according to claim 14, wherein said secondnon-carbon material is a second titanium compound.
 16. The capacitoraccording to claim 14, wherein said second non-carbon material istitanium.